Particle shield

Abstract

A vacuum processing system for processing semiconductor wafers includes a particle shield (16) disposed above the wafer (10) to block moving particles in a vacuum chamber which would otherwise contact the wafer (10). The particle shield (16) is attached to arm (18), allowing the particle shield (16) to be moved away from the wafer or photomask during processing.

What is claimed is: 
     
       1. Apparatus for preventing adhesion of foreign particles to a surface during vacuum chamber processing, comprising: a shield for blocking the particles; and   positioning means connected to said shield for maintaining said shield a predetermined distance from the surface in order to prevent contact of particles with the surface.   
     
     
       2. The apparatus of claim 1, wherein said shield comprises a substantially flat plate which is impervious to the foreign particles. 
     
     
       3. The apparatus of claim 1 wherein said shield is dimensioned to extend beyond the perimeter of the surface. 
     
     
       4. The apparatus of claim 1 wherein said shield is formed from aluminum or stainless steel. 
     
     
       5. The apparatus of claim 1 wherein said shield is formed from quartz. 
     
     
       6. The apparatus of claim 1, wherein the surfaces of said shield are polished to a mirror finish. 
     
     
       7. The apparatus of claim 6, wherein said shield has a polished finish of about one micron rms. 
     
     
       8. The apparatus of claim 1, wherein said shield further comprises at least one side guard disposed about the edge of said shield to further protect the surface from contact with the particles. 
     
     
       9. The apparatus of claim 1, further comprising adjusting means for enabling movement of said positioning means such that said shield may be temporarily moved away from the surface during processing and returned to its position beside the surface during other times. 
     
     
       10. Apparatus for preventing adhesion of small, moving particles to the surface of a semiconductor wafer or photomask during vacuum chamber processing, comprising: a shield impervious to the particles;   a robotic arm connected to said shield for positioning said shield at a location closely adjacent but not touching the surface;   control means for controlling movement of said robotic arm; and   a platform for holding the wafer or photomask at a desired position.   
     
     
       11. The apparatus of claim 10, wherein said robotic arm comprises a first robotic arm means, and said control means comprises a first control means, and further comprising: a second robotic arm for positioning said platform means; and   second control means for controlling the position of said second arm.   
     
     
       12. A system for vacuum processing wherein foreign particles are shielded from the surface being processed, comprising: a vacuum chamber in which a low pressure may be created for processing of the surface;   a cassette for holding a plurality of devices having surfaces to be processed;   a platform for receiving and positioning the devices;   a shield for shielding a surface of the device on said platform;   a shield arm for positioning said shield closely adjacent the surface to prevent contact of foreign particles with the surface; and   a shield arm controller for controlling the movement of said shield arm.   
     
     
       13. The processing system of the claim 12, wherein said vacuum chamber comprises a first vacuum chamber and further comprising a second vacuum chamber separated from said first vacuum chamber by a valve. 
     
     
       14. The processing system of claim 13, wherein said shield comprises a first shield and further comprising: a second shield for being disposed adjacent a surface in said second chamber; and   positioning means for positioning said second shield in said second chamber.   
     
     
       15. The processing system of claim 12, wherein said cassette has closed ends to protect the devices from moving particles within said first chamber. 
     
     
       16. The processing system of claim 12, further comprising platform arm means for positioning said platform means. 
     
     
       17. A method of preventing adhesion of small foreign particles on the surface of a device during vacuum processing comprising the steps of: positioning the device at a predetermined position during the vacuum processing; and   positioning a particle impervious shield adjacent to the surface undergoing processing, said shield being a fixed distance from and positioned sufficently close to the surface to prevent contact by the particles to the surface.   
     
     
       18. A method for processing semiconductor wafers, comprising the steps of: supporting a plurality of semiconductor wafers in a wafer cassette located in a first vacuum chamber;   reducing the pressure in said first vacuum chamber to a low pressure;   reducing the pressure in a second vacuum chamber to a low pressure;   removing a wafer from said cassette and positioning said wafer in a desired position for processing;   positioning a particle shield closely adjacent the surface of said wafer undergoing processing, such that small, moving foreign particles within said first chamber are prevented from contacting said surface;   moving said wafer and said shield from said first chamber to said second chamber; and   processing said wafer.   
     
     
       19. The method of claim 18, further comprising the steps of: moving said shield away from said wafer before processing said wafer; and   repositioning said shield beside the processed surface of said wafer before returning said wafer to said cassette.